It is critically important to monitor aircraft performance during take-off so that a pilot will know as soon as possible if he/she can not take off safely. The pilot needs to detect inadequate take-off performance at low speeds during the early part of the take-off roll. If he waits too long, the pilot may not be able to take-off in the remaining runway, nor can he stop in the remaining distance. At that point, such information is not very useful. Even though the pilot understands the need for early take-off performance evaluation, it is very difficult for the pilot to detect inadequate performance at low speeds during the early ground roll.
Numerous devices have been proposed to help a pilot monitor take-off performance but, to date, these devices have not proved themselves to be very useful. One problem with many such devices is that they assume that the aircraft is capable of a certain performance which is sometimes referred to as "handbook" performance. That is, these devices assume that the aircraft will have a certain amount of thrust, lift, air drag and rolling drag. In reality, all of these factors will vary from plane to plane. No known device operates to learn the performance characteristics of the airplane in which it is mounted.
In addition to the different flight characteristics of every plane, each pilot will fly the plane slightly differently from other pilots. For example, engine settings for take-off will vary from pilot to pilot. To make a meaningful and early prediction of inadequate take-off performance, a monitor must take all of these variables into consideration. Known monitors do not have the ability to acquire and utilize these parameters.
A pilot, of course, does have the ability to learn the unique operating characteristics of each plane and pilot, but the number of factors influencing take-off performance make it very difficult to detect inadequate performance at low speeds during the early part of the take-off roll. The acceleration of an aircraft during take-off is affected by numerous factors including weight of the aircraft, air temperature, air pressure, power settings, rolling resistance and others. These numerous factors make the pilot's job of judging take-off performance very complex. The ability of a pilot to judge take-off performance is further hampered by the fact that he flies different planes that have different characteristics. Thus, the job of judging take-off performance at low speeds remains difficult and uncertain.